I’ve been following the keratin treatment threads that proliferated before Christmas and have been umming and ahhing over going back to getting regular treatments after a year’s break. The cost (£230 in my local salon for my elbow length hair) puts me off, along with the fact it doesn’t completely get rid of frizz 
Anyway as a last ditch effort before I went ahead and booked one, I bought this:
Color Wow Dream Coat
It’s a heat activated spray - you apply it on damp hair before blow drying. I spritzed it around (not v carefully) and then did the ‘reverse blow dry’ as per Sarah Angius (link here).
That was 4 days ago. Since then, I’ve had the best hair of my actual life! The weather has thrown everything at my hair - rain, sleet, snow, wind - and it’s remained smooth and glossy. And then I washed it today, and just used my normal heat protectant (not the magic spray) to blow dry. The magic color wow spray appears to still be working despite shampoo and conditioning and it took me approx 10 mins to dry my hair into shiny, hair-advert hair.
My hair is not shiny, hair-advert hair. I have long frizzy, fine, dry straw. Tbh I am slightly agog at what chemicals must have coated my hair to result in this apparent transformation but, I don’t care swish and I thought you should all know. If you’re considering forking out for a keratin treatment and don’t mind faffing about for 10 mins with a round brush as per the YouTube clip, it’s worth a try. Your mileage may vary, etc etc..